What is passwordless authentication?
Passwordless authentication verifies identity without a password, using passkeys, magic links, hardware keys, or biometrics. It dramatically reduces credential-based attacks but doesn’t protect the session cookies and tokens issued after login – which remain vulnerable to session hijacking and AitM phishing.
The shared blind spot across every passwordless method
All passwordless methods converge on the same outcome: after a successful login, the app issues a session cookie (and often a refresh token) to keep the user authenticated. Protecting the front door doesn’t protect what it hands out. Attackers exploit this two ways:
- Session hijacking via infostealers – malware reads the post-authentication cookie from browser storage, stealing the output of authentication instead of attacking the input.
- AitM phishing – a proxy captures the session cookie even after a legitimate passkey or biometric login.
Can my organization’s sessions still be stolen after going passwordless?
Run Check Your Exposure to see whether session cookies tied to your domain can still be stolen even after going passwordless. Going passwordless does not stop infostealers from lifting active session cookies, which let attackers bypass login entirely, and SpyCloud surfaces these exposures.
What passwordless programs still need: session-layer monitoring
AitM toolkits have evolved specifically to work against passwordless flows, so the missing piece is a layer that watches the session itself:
- Method doesn’t matter to AitM. It captures the session cookie no matter what generated it – passkey, biometric, or token.
- Passkey-only orgs aren’t immune. They carry the same session-layer exposure as password-based ones.
- Watch the session, not just the login. Detect stolen cookies and refresh tokens in criminal markets and invalidate them before use.
- Complete the picture. SpyCloud Session Identity Protection recaptures those artifacts – including from passwordless flows – and automates session invalidation.
Passwordless methods compared
“Passwordless” covers several methods with different security properties but a shared session-layer gap:
- Passkeys – device-bound public-key credentials; the strongest option and phishing-resistant at the login step.
- Hardware security keys – physical FIDO2 tokens, similarly phishing-resistant but with provisioning overhead.
- Biometrics – convenient, though usually unlocking a local credential rather than replacing the flow outright.
- Magic links and OTPs – passwordless in name, but still phishable and weaker than the cryptographic options.
However strong the method, all of them issue a session cookie after login – the artifact AitM phishing and infostealers target no matter how the user authenticated.
Passwordless does not stop stolen session cookies.
See whether sessions tied to your domain are exposed.
Frequently Asked
It’s significantly more secure than passwords against phishing, brute force, credential stuffing, and reuse. But it doesn’t eliminate session hijacking: every method issues a session cookie after login, and that cookie can be stolen by infostealer malware or captured by AitM phishing – bypassing the authentication method without attacking it directly.
Yes. AitM proxies sit between the user and the real login. The user completes the passwordless challenge normally, but the proxy captures the resulting session cookie before it’s stored. The attacker ends up with a valid post-authentication session. AitM is method-agnostic – it captures the session artifact regardless of whether a password, passkey, hardware token, or magic link produced it.
Yes. Passwordless eliminates the largest category of credential-based attacks and should be deployed – it’s just not complete on its own. Pair it with session-layer monitoring that detects and invalidates stolen cookies and refresh tokens, and you cover both the authentication step and the session it creates.